Decalcification of magnesian dolomites



Jan. 21, 1936. c. D.` wYGAL 2,028,639

.DECALCIFICATION OF MAGNESIAN DOLOMITES Filed oct. 26, 19541 Patented Jan. 21, 1936 'l Y A .K

" .UNITED STATES, PATENT oFFlcE DECALCIFICATION F MAGNESIAN DOLOlVIITES Clyde Douglas Wygal, Manistique, Mich., assignor to Inland Lime and Stone Companma corporation of Michigan Application October 26, 1934, Serial No. 750,207 7 Claims. (Cl. 23-130) This invention relates to a process for decalcichlorinated lime is at rst dissolved in water and cation of magnesian dolomites. then separated.

Magnesian rocks have heretofore been substan- The drawing illustrates the process in flowtially valueless as a source of magnesia and magsheet form. IleSllm COmDOllIldS Owing t0 the difficulty and ex- As an example of the invention, calcine dolo- Dense 0f Separating the calcium therefrom. mite, or impure magnesia, containing 38.60% While authorities such as Mellor in Organic magnesium oxide, 59% calcium oxide, 1.35% and Theoretical Chemistry, vol. IV, pages 281-2, oxides of iron and aluminum, and 0.7% silica, have suggested the removal of calcium from was hydrated and chlorinated. The resulting 10 magnesia by the use of hydrochloric acid or sulmagnesian sludge, on a dehydrated basis, showed 1()v iuric acid, itl has always been conceded by the 91.74% magnesium oxide, 4.05% calcium oxide, trade and by these authorities that chemical 2.46% oxides of iron and aluminum, Vand 1.30% purification of dolomites was commercially imsilica. The chlorinated lime producedhad subpossible. stantially no magnesia content which could be By means of the present invention, however, detected upon analysis. 1 it is possible not only to prepare substantially The lime content may be lowered below 4%,

pure magnesium compounds (say 90% magnesia but as the lime is removed, the decrease in alkaor more) from low magnesia dolomites, but also linity promotesV the formation of chlorates. In to utilize fully the calcium present. The method the normal production of calcium hypochlorite is commercially feasible for the first time bethis is a disadvantage, but if it is desired to pro- 20 cause of the fact that the calcium product, induce a purer magnesia the calcium hypochlorite stead of being valueless as heretofore, is of high solution may be decanted toward the end of the value as well as purity. operation, and the chlorination continued re The invention is particularly valuable for maggardless of the formation or chlorates.

nesian dolomites having a magnesia content of The magnesia thus produced has particular 25 22% or upwards and particularly contents from value for the production of bisulte liquor, a1- 22-44%. The content of non-magnesian and though the hydrate may be used for any comcalcium oxides should be less than 10% of the mercial purposes. In preparing bisulfite solumagnesia, but this is ordinarily the case in magtion, the magnesian sludge is diluted with water nesian dolomites. to produce a milk of magnesia oi.' the desired 30 In accordance with the present invention, the specic gravity. This is then sulfuretted in the dolomite is calcined and is then chlorinated in desired manner, generally by scrubbing the milk accordance with any of the known processes. 0f magnesia in towers with sulfur dioxide (SO2). This is customarily done by carefully hydrating The solution, the base of which is almost entirethe material, preparing a milk of lime of the dely magnesia as Mg(HSO3)z, is more desirable 35 sired specific gravity, and then chlorinating the than the bisuliite solution now in use in the milk of lime until substantially all of the calcium sulte pulp and paper industries. oxide has been chlorinated to produce Ca(OCl)2, The foregoing detailed description has been suiicient alkalinity being maintained to prevent given for clearness of understanding only, and

the formation of chlorates or chlorides. For some no unnecessary limitations should be understood 0 i reason not clearly understood the magnesia protherefrom, but the appended claims should be duced by calcining high magnesian rocks does not construed as broadly as permissible in view of hydrate appreciably upon the addition of water, the prior art. but remains as oxide. However, during the What I regard as new and desire to secure by chlorination operation hydration may occur. At Letters Patent is: 5 the end of this procedure the calcium hypo- 1. The method of utilizing magnesian rocks @merite wi11 all be in solution and the residuum, high in magnesia content. which comprises calconsisting of a magnesium hydrate sludge, is alcining the rock to produce a mixture of calcium lowedto settle and the liquid is then decanted and magnesium oxides, adding water thereto to or removed by any known method, or it may be hydrate the calciuml oxide, chlorinating the r'e- 50 filtered or filter-pressed to separate the matesulting calcium hydroxide in the presence of rials. The resulting magnesium hydrate sludge water to produce a solution of calcium hypomay then be washedwith water and settled or chlorite, the chlorination being stopped when filtered as required. If chlorination is carried out substantially all the calcium and substantially by one of the substantially dry methods, the none of the magnesium has been chlorinated, 55

and separating the unchlorinated magnesia from the solution.

2. The method as set forth in claim 1, in which the calcined rock contains at least 22% MgO.

3. The method as set forth in claim l, in which the calcined rock contains of the order of 22-44% MgO.

4. The method as set forth in claim 1 in which the calcined rock contains at least 22%v MgO and the insoluble impurities are not greater than 10% of the amount of the magnesia.

5. In the method of preparing magnesium bisulphite from a high magnesian rock containing calcium, the steps of calcining the rock to produce a mixture of calcium and magnesium oxides, adding Water to the oxides and chlorinating the resulting mixture to chlorinate substantially al1 of the calcium without chlorinating substantial amounts of the magnesia, separating the residual magnesia, and treating it withsulphur dioxide to produce magnesium bisulphite.

6. The method as set forth in claim 5, in which the oalcined rock contains of the order of 22-44% magnesium oxide.

7. The method as set forth in claim 5, in which the calcined rock contains of the order of 22-44% magnesium oxide, and the insoluble impurities do not exceed 10% of the amount of the magnesia.

CLY'DE DOUGLAS WYGAL. 

